EV Digest 6768
Topics covered in this issue include:
1) Re: Vehicle efficiency, wh/mile - cruise control
by "Roland Wiench" <[EMAIL PROTECTED]>
2) Re: How does a 48v motor handle higher voltages?
by "(-Phil-)" <[EMAIL PROTECTED]>
3) Re: Sepex regen
by "(-Phil-)" <[EMAIL PROTECTED]>
4) Re: How does a 48v motor handle higher voltages?
by "(-Phil-)" <[EMAIL PROTECTED]>
5) Re: BMS (Battery Management System (Was: 1-Wire Expertise)
by Danny Miller <[EMAIL PROTECTED]>
6) Re: BMS (Battery Management System (Was: 1-Wire Expertise)
by "(-Phil-)" <[EMAIL PROTECTED]>
7) Re: Sepex regen
by tt2tjw <[EMAIL PROTECTED]>
8) My Watt-hour / mile with comments on battery cycle life and DOD
by Steve Powers <[EMAIL PROTECTED]>
9) Re: Noodling Lithium prices and batteries
by "Jay Caplan" <[EMAIL PROTECTED]>
10) Re: magnetic field in EV car?
by Tehben Dean <[EMAIL PROTECTED]>
11) Re: How does a 48v motor handle higher voltages?
by Lee Hart <[EMAIL PROTECTED]>
12) Re: BMS (Battery Management System (Was: 1-Wire Expertise)
by Danny Miller <[EMAIL PROTECTED]>
13) Re: Vehicle efficiency, wh/mile
by "jerryd" <[EMAIL PROTECTED]>
--- Begin Message ---
If you was on a dead level grade, cruise controls works, as it does in my
other cars, but in hilly country while going up a grade, you can feel more
power being added which is pushing the accelerator harder, and going down
hill, it holds you back.
I make more range, while holding the accelerator at a constant pressure
which may slow you up a bit, and let it get up to a high as a speed as
possible while coasting down a grade.
At one time we did not have a speed limit, now it is 79 mph, (4 miles over),
where at times a vehicle may get up to over 85 mph going down hill, which I
therefore can roller coast up the next which slows the vehicle to about 60
mph going up the next grade.
I was be able to coast all the way from my work place all the way into my
garage which was about 5 miles.
I now have too many short runs of about 1/2 mile long with only one stop at
the end of each run. It's like driving on a very long 3 to 5 mile long
connected parking lot.
Roland
----- Original Message -----
From: "Tehben Dean" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, May 13, 2007 12:03 PM
Subject: Re: Vehicle efficiency, wh/mile - cruise control
> It seems like cruise control would be very easy to build into an EV
> controller... its all electronic.
> Wonder why its not done... or is it?
>
> On May 13, 2007, at 6:49 AM, [EMAIL PROTECTED] wrote:
>
> >
> > Roland> One way I found that can reduce the AH or wh usage is if
> > Roland> everything else is perfect, is the amount of pressure you
> > Roland> maintain on the accelerator. For example, to accelerate
> > my EV up
> > Roland> to a certain speed, I just press the accelerator just
> > to that
> > Roland> point which will maintain that speed, not push it to
> > the floor
> > Roland> and then when you get to the speed you want, then let
> > up on the
> > Roland> accelerator at that point.
> >
> > Seems like cruise control would be very helpful in an EV.
> >
> > --
> > Skip Montanaro - [EMAIL PROTECTED] - http://www.webfast.com/~skip/
> >
>
>
--- End Message ---
--- Begin Message ---
Typically a 48v motor (non-PM) can withstand 96v for short durations. Keep
it cool and you can do a lot of abusing! Too high of power and you may fry
the brushgear/commutator though.
I've even heard of people sealing the motors up and immersing them in
oil.... You'll get friction from the oil shear, but if you have an oil
cooler, it's definitely going to say cool!
Some large truck and bus alternators are cooled in this way also.
The Prius uses oil-cooled motors, and they are tiny! 600 volts!
Tell him you are going to add oil cooling.... =)
-Phil
----- Original Message -----
From: "childreypa" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, May 13, 2007 10:08 AM
Subject: How does a 48v motor handle higher voltages?
I've been calling some forklift places trying to find an old motor that
I can use to get my project going. I am looking for a large forklift
motor at 48v. I mentioned that this was for an electric vehicle running
greater than 96v. The man said I couldn't do this. A 48v motor can only
handle 48v. This makes perfect sense but I know people use them in EV's.
Is it the better cooling these motors receive in a car? Advancing the
brushes? Maybe the motor has to be rewound? Maybe the life is severely
deminished? How do I answer an oldtimer who knows plenty more than me
about motors that I want to use a 48v motor in an EV?
Thanks,
Paul
--- End Message ---
--- Begin Message ---
For an interesting bunch of reading on motor controllers, and many things EV
related, check out Richard Torrens' excellent site:
http://4qd.co.uk/faq/index.html
Tons of great reading, and explanations on things like how the motor
inductance is used to act as a boost during regen.
-Phil
----- Original Message -----
From: "tt2tjw" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, May 13, 2007 11:08 AM
Subject: Re: Sepex regen
Ok thanks again George, I'm off to read about inductance then hopefully I
will understand a little better how it works and how to choose the duty
value.
George Swartz wrote:
In PWM boost, the low side IGBT turns on and builds up armature current.
When it turns off, the "flywheel" effect of the armature inductance
causes current to keep flowing thru a blocking diode and back into the
battery. (The current waveform is a two slope, and roughly triangular at
50% duty cycle) This flyback current would flow up to any practical
battery voltage.
At very low motor voltages, the boost becomes inefficient, but electrical
braking remains good, as energy is dissipated in the motor windings.
Sometimes, an external inductor is used to add inductance to the motor.
This is particularly true for a sepex motor since it has no series field
to add to motor inductance. The external inductor makes both the boost
and run more efficient.
The flyback diode could be the inverse parallel diode associated with the
upper IGBT, or could be an added diode?
On Sun, 13 May 2007 17:39:12 +0100, tt2tjw wrote
Thanks for your help George, I think I partially understand it now
I originally stupidly thought that at low rpm there was too high a
voltage, in actual fact there is too little volts to charge the battery.
I am still a little confused though, how does the chopper boost the
voltage?
I can have a guess based on what I can see in the controller;
This is how the controller is set up:
the IGBT driving the armature is a half bridge C1 is connected to +ve
battery
E1/C2 is connected to one of the armature terminals
E2 is connected to the other armature terminal and to the -ve battery
terminal there are the usual free wheel diodes between E2 and E1/C2 and
between E1/C2 and C1
As far as I can see:
when the battery is driving the motor the low side is turned off and
the high side is chopping (up to 1500rpm, thereafter the high side is
full on) in high rpm regen both the high and the low side are turned off
in low rpm regen the high side is off and I think the low side must
chop.
In low rpm regen when the low side is on the current will flow though
the low side IGBT and back through the armature. Does this somehow
increase the voltage in the armature untill it is large enough to charge
the battery?
What would happen if the low side didn't chop?
George Swartz wrote:
You need both. The chopper is probably a "shunt" boost chopper which
is
in
parallel with the motor and is used when the motor back emf is less
than
the
battery voltage. The chopper boosts the lower motor voltage up to the
battery voltage. Regen braking is strong and effective down to low
speed,
like 3 mph or so. At high speeds, if you used a chopper, it would have
to
be in a series configuration with the batteries, assuming you were
stuck with full field. It is easy to use field control in the sepex
motor for regen above base speed.
On Sun, 13 May 2007 15:45:35 +0100, tt2tjw wrote
Does anyone know why it might be neccessary to chop the regen current
on a sepex motor?
Below is my understanding, do other people think this is correct?
I can see that the regen current/volts must be limited to avoid
cooking the batteries.
It seems to me that at high rpm this can be achieved by varying the
field current until max field current is reached (which for my motor
is about 1500 rpm or about 15mph). As the rpm drops below this level
one way to limit the regen current would be to open the main
contactor, presumably this is not something one would want to do on a
regular basis and so the regen current is chopped.
If my understanding is correct the brake chopper only needs to work
below 1500rpm, though it could also be used at higher rpm. At higher
rpm which method is better, varying the field current or chopping the
regen current?
--- End Message ---
--- Begin Message ---
Oh, I forgot to say, the reason I said non-PM is because if you overdrive a
PM motor, you can actually demagnetize or depolarize the magnets!
-Phil
----- Original Message -----
From: "(-Phil-)" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, May 13, 2007 11:38 AM
Subject: Re: How does a 48v motor handle higher voltages?
Typically a 48v motor (non-PM) can withstand 96v for short durations.
Keep it cool and you can do a lot of abusing! Too high of power and you
may fry the brushgear/commutator though.
I've even heard of people sealing the motors up and immersing them in
oil.... You'll get friction from the oil shear, but if you have an oil
cooler, it's definitely going to say cool!
Some large truck and bus alternators are cooled in this way also.
The Prius uses oil-cooled motors, and they are tiny! 600 volts!
Tell him you are going to add oil cooling.... =)
-Phil
----- Original Message -----
From: "childreypa" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, May 13, 2007 10:08 AM
Subject: How does a 48v motor handle higher voltages?
I've been calling some forklift places trying to find an old motor that
I can use to get my project going. I am looking for a large forklift
motor at 48v. I mentioned that this was for an electric vehicle running
greater than 96v. The man said I couldn't do this. A 48v motor can only
handle 48v. This makes perfect sense but I know people use them in EV's.
Is it the better cooling these motors receive in a car? Advancing the
brushes? Maybe the motor has to be rewound? Maybe the life is severely
deminished? How do I answer an oldtimer who knows plenty more than me
about motors that I want to use a 48v motor in an EV?
Thanks,
Paul
--- End Message ---
--- Begin Message ---
I don't think there's any practicality to using IRDA. You generally
need a straight line-of-sight.
Again, the 1-wire protocol CAN be adapted to an isolated scheme,
however, no commercially available device will implement it. You'd need
to write up an implementation. It just takes a controller (PIC) and two
optoisolators (might be $1 or $2). So you can power a PIC voltage
sensor with the battery voltage and then communicate that across the
isolated bus.
There's a question of how much power the sensor draws. It's not much
but the important problem here is that with one hooked up to each batt
it's generally impractical to disconnect each one when you're not
driving. The PIC may be able to go into SLEEP mode and its current goes
way into inconsequential. However, the typical voltage divider must
remain powered and that draws about 2.5mA. The optoisolator's receiving
side also has a nonzero "dark current" when the receiving side is
powered even if it's at the "off" level.
Well, 2.5mA isn't a particularly big problem. It would take months to
use a substantial portion of the batt capacity.
The boards should logically integrate the charging regs on-board, since
we're already building one per batt.
Danny
(-Phil-) wrote:
I used the TSOP1740 in a project a few years ago. I think I bought
100 of them for about 40 cents each. Pretty cheap!
http://www.vishay.com/docs/82030/82030.pdf
You may be thinking of FastIR/IRDA or similar. Too costly, and no
need to invoke the complex protocols.
The Micros can be very small/low power. The protocol is very simple
because of the low data rate requirement. I can do it in a few
hundred lines of assembly code, and run it on a ring-clocked low power
micro.
It's probably easier, cheaper, and more reliable to use IR rather than
visible. The components ate cheap, and the modulated IR will bounce
better and not suffer as many from problems from interference. They
work fine even in the presence of sunlight.
If I build it, I will open-source it. Hurray if others want to build
them using my code! If more DIY EV'ers had a BMS, we'd save a lot of
batteries!
-Phil
----- Original Message ----- From: "Lee Hart" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Saturday, May 12, 2007 2:26 AM
Subject: Re: BMS (Battery Management System (Was: 1-Wire Expertise)
This is a good idea, Phil. I've used visible light in a battery box,
and it worked pretty well. The box had white styrofoam lining it, and
the light bounced around nicely, so a single sensor could see the
light from any sender.
I wonder about the cost, though. The IR receivers I see cost dollars,
not pennies. Do you have any examples in mind? Also, the micro may
need to be more powerful than you think; network protocols often
require a large amount of computing resources.
An open source project is a worthy goal, but too often people use the
name to mean, "I want somebody else to develop it for me for free."
I'm not sure how to inspire a group of people to work together on
such a project.
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
(¤Phil¤) wrote:
Seems like the right thing to do is put a little board on each
battery. The board would contain a small microcontroller with ADC, a
IR LED, a monolithic IR receiver (like those used in consumer
electronics to receive remote control signals), a high-current
MOSFET and a resistor (light bulb?). The board would only hook to
(+) and (-) of each battery in the array. No data cabling. 2
wires, that's it.
The units would all be identical, but contain a unique serial number
in the firmware. A central controller would then poll the
individual units via 40khz IR signals. The units would respond the
same way. The central controller can then order the load on and off
for equalization of the pack when charging.
The IR effectively galvanically isolates the whole mess and makes it
unlikely an accident could occur. The IR would readily bounce all
around battery enclosures and make a reliable 2-way communication
system with no wires and very low cost. The IR LED/Receiver are
commodity items and cost pennies.
The little boards would thus be cheap and easy to make, and very
safe with no possibility of shorts, etc.
Open-source the firmware and PCB design. Maybe a group-buy of the
little PCBs.
--- End Message ---
--- Begin Message ---
Note, I didn't specify IIRDA!
I recommend 40khz IR. Same stuff used in consumer electronics for remote
controls. You don't need LOS. No cabling and you can pot the whole
assembly so no battery acid can get on your board or the data connectors.
Only cabling in the battery box will then be the primary wiring.
-Phil
----- Original Message -----
From: "Danny Miller" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, May 13, 2007 12:04 PM
Subject: Re: BMS (Battery Management System (Was: 1-Wire Expertise)
I don't think there's any practicality to using IRDA. You generally need a
straight line-of-sight.
Again, the 1-wire protocol CAN be adapted to an isolated scheme, however,
no commercially available device will implement it. You'd need to write
up an implementation. It just takes a controller (PIC) and two
optoisolators (might be $1 or $2). So you can power a PIC voltage sensor
with the battery voltage and then communicate that across the isolated
bus.
There's a question of how much power the sensor draws. It's not much but
the important problem here is that with one hooked up to each batt it's
generally impractical to disconnect each one when you're not driving. The
PIC may be able to go into SLEEP mode and its current goes way into
inconsequential. However, the typical voltage divider must remain powered
and that draws about 2.5mA. The optoisolator's receiving side also has a
nonzero "dark current" when the receiving side is powered even if it's at
the "off" level.
Well, 2.5mA isn't a particularly big problem. It would take months to use
a substantial portion of the batt capacity.
The boards should logically integrate the charging regs on-board, since
we're already building one per batt.
Danny
(-Phil-) wrote:
I used the TSOP1740 in a project a few years ago. I think I bought 100
of them for about 40 cents each. Pretty cheap!
http://www.vishay.com/docs/82030/82030.pdf
You may be thinking of FastIR/IRDA or similar. Too costly, and no need
to invoke the complex protocols.
The Micros can be very small/low power. The protocol is very simple
because of the low data rate requirement. I can do it in a few hundred
lines of assembly code, and run it on a ring-clocked low power micro.
It's probably easier, cheaper, and more reliable to use IR rather than
visible. The components ate cheap, and the modulated IR will bounce
better and not suffer as many from problems from interference. They work
fine even in the presence of sunlight.
If I build it, I will open-source it. Hurray if others want to build
them using my code! If more DIY EV'ers had a BMS, we'd save a lot of
batteries!
-Phil
----- Original Message ----- From: "Lee Hart" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Saturday, May 12, 2007 2:26 AM
Subject: Re: BMS (Battery Management System (Was: 1-Wire Expertise)
This is a good idea, Phil. I've used visible light in a battery box, and
it worked pretty well. The box had white styrofoam lining it, and the
light bounced around nicely, so a single sensor could see the light from
any sender.
I wonder about the cost, though. The IR receivers I see cost dollars,
not pennies. Do you have any examples in mind? Also, the micro may need
to be more powerful than you think; network protocols often require a
large amount of computing resources.
An open source project is a worthy goal, but too often people use the
name to mean, "I want somebody else to develop it for me for free." I'm
not sure how to inspire a group of people to work together on such a
project.
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
(¤Phil¤) wrote:
Seems like the right thing to do is put a little board on each battery.
The board would contain a small microcontroller with ADC, a IR LED, a
monolithic IR receiver (like those used in consumer electronics to
receive remote control signals), a high-current MOSFET and a resistor
(light bulb?). The board would only hook to (+) and (-) of each
battery in the array. No data cabling. 2 wires, that's it.
The units would all be identical, but contain a unique serial number in
the firmware. A central controller would then poll the individual
units via 40khz IR signals. The units would respond the same way. The
central controller can then order the load on and off for equalization
of the pack when charging.
The IR effectively galvanically isolates the whole mess and makes it
unlikely an accident could occur. The IR would readily bounce all
around battery enclosures and make a reliable 2-way communication
system with no wires and very low cost. The IR LED/Receiver are
commodity items and cost pennies.
The little boards would thus be cheap and easy to make, and very safe
with no possibility of shorts, etc.
Open-source the firmware and PCB design. Maybe a group-buy of the
little PCBs.
--- End Message ---
--- Begin Message ---
thanks phil, I quite often read articles from 4qd, I will look again
for inductance.
(-Phil-) wrote:
For an interesting bunch of reading on motor controllers, and many
things EV related, check out Richard Torrens' excellent site:
http://4qd.co.uk/faq/index.html
Tons of great reading, and explanations on things like how the motor
inductance is used to act as a boost during regen.
-Phil
----- Original Message ----- From: "tt2tjw" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, May 13, 2007 11:08 AM
Subject: Re: Sepex regen
Ok thanks again George, I'm off to read about inductance then
hopefully I will understand a little better how it works and how to
choose the duty value.
George Swartz wrote:
In PWM boost, the low side IGBT turns on and builds up armature
current. When it turns off, the "flywheel" effect of the armature
inductance causes current to keep flowing thru a blocking diode and
back into the battery. (The current waveform is a two slope, and
roughly triangular at 50% duty cycle) This flyback current would
flow up to any practical battery voltage.
At very low motor voltages, the boost becomes inefficient, but
electrical braking remains good, as energy is dissipated in the
motor windings.
Sometimes, an external inductor is used to add inductance to the
motor. This is particularly true for a sepex motor since it has no
series field to add to motor inductance. The external inductor
makes both the boost and run more efficient.
The flyback diode could be the inverse parallel diode associated
with the upper IGBT, or could be an added diode?
On Sun, 13 May 2007 17:39:12 +0100, tt2tjw wrote
Thanks for your help George, I think I partially understand it now
I originally stupidly thought that at low rpm there was too high a
voltage, in actual fact there is too little volts to charge the
battery.
I am still a little confused though, how does the chopper boost the
voltage?
I can have a guess based on what I can see in the controller;
This is how the controller is set up:
the IGBT driving the armature is a half bridge C1 is connected to
+ve battery
E1/C2 is connected to one of the armature terminals
E2 is connected to the other armature terminal and to the -ve
battery terminal there are the usual free wheel diodes between E2
and E1/C2 and between E1/C2 and C1
As far as I can see:
when the battery is driving the motor the low side is turned off
and the high side is chopping (up to 1500rpm, thereafter the high
side is full on) in high rpm regen both the high and the low side
are turned off in low rpm regen the high side is off and I think
the low side must chop.
In low rpm regen when the low side is on the current will flow
though the low side IGBT and back through the armature. Does this
somehow increase the voltage in the armature untill it is large
enough to charge the battery?
What would happen if the low side didn't chop?
George Swartz wrote:
You need both. The chopper is probably a "shunt" boost chopper
which is
in
parallel with the motor and is used when the motor back emf is
less than
the
battery voltage. The chopper boosts the lower motor voltage up to
the battery voltage. Regen braking is strong and effective down
to low
speed,
like 3 mph or so. At high speeds, if you used a chopper, it would
have
to
be in a series configuration with the batteries, assuming you were
stuck with full field. It is easy to use field control in the
sepex motor for regen above base speed.
On Sun, 13 May 2007 15:45:35 +0100, tt2tjw wrote
Does anyone know why it might be neccessary to chop the regen
current on a sepex motor?
Below is my understanding, do other people think this is correct?
I can see that the regen current/volts must be limited to avoid
cooking the batteries.
It seems to me that at high rpm this can be achieved by varying
the field current until max field current is reached (which for
my motor is about 1500 rpm or about 15mph). As the rpm drops
below this level one way to limit the regen current would be to
open the main contactor, presumably this is not something one
would want to do on a regular basis and so the regen current is
chopped.
If my understanding is correct the brake chopper only needs to
work below 1500rpm, though it could also be used at higher rpm.
At higher rpm which method is better, varying the field current
or chopping the regen current?
--- End Message ---
--- Begin Message ---
In my 93 Festiva, lightened with all extra parts taken
off (back seat and other unnecessary stuff)
9" ADC
120 V
10 x 12 V pack
550 A controller
I calculated about 200 Wh/mile average with stop and
start, speeds 0 - 45 MPH, hills, some coasting, lots
of stops and starts. Relatively lead footed
acceleration (using 550 A controller).
I did this by driving 2 miles, stopping for 3 hours,
measuring the resting voltage, driving another 2
miles, recharging at exactly 6 A rate for exactly 30
minutes, driving another 2 miles, resting for 5 hours,
and rechecking the voltage.
The voltage just before adding the 6 A for 30 min
charge was nearly identical to the voltage after the
charge + 2 mile drive + 5 hour rest. Also, it is
consistent with other measurements I have made.
So, with my 120 V system ...
2 miles = 3 Ah (in my 120 V pack)
120 V * 3 Ah / 2 miles = 180 Wh / mile.
I adjusted it slightly and rounded to 200 Wh / mile.
As for my range, I don't want to go anywhere near 80%
DOD. I don't even want to go 50% DOD. After 8 - 10
miles and rest to recove the batts, they sit at about
12.5 V. Thats about 60% SOC, 40% DOD for flooded
lead. To be safe, I won't take it over 12 miles.
That's the thing about range. Even the experienced
experts agree, you need a lot more range built in than
you will typically use.
A car designed for 40 miles (absolute max and you are
killing the pack), don't regurarly take over 20 miles
unless you want to replace your batte every year.
That's where it seems that nearly everyone, especially
people new to EV's go wrong. Oh, I have a 40 mile
range, I'll do that every day. A few months later,
the pack is totally dead. Why? It wasn't designed
fot that kind of abuse.
If you need 20 miles, design for 60 miles. If you
need 40 miles, Design for 100 miles. If you need 50 -
60 miles, you are going to be buying a lot of
batteries and often.
Hope that helps.
Steve
____________________________________________________________________________________Take
the Internet to Go: Yahoo!Go puts the Internet in your pocket: mail, news,
photos & more.
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--- End Message ---
--- Begin Message ---
Math correction
> $2.75/lb. The amount
> of lithium metal in lithium carbonate is about 11/58. So that brings
> the Lithium metal cost to about $80 per lb (per 453.59 g).
Li2CO3 is mol wt 74. The Li2 is 14 mol wt
So, the fraction is 14/74 of lithium as fraction of lithium carbonate
$2.75 divided by 14 x 74 = $14.5/lb of lithium metal, not $80
> So, a 50AH Lithium cell has ~15g of Lithium metal in it. Which comes
> out to about $2.65.
15 divided by 453 x $14.50 = $0.48 of lithium in the 50AH battery, not $2.65
JLC
----- Original Message -----
From: "Timothy Balcer" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, May 13, 2007 12:56 PM
Subject: Noodling Lithium prices and batteries
> I was curious as to how much actual Lithium was in the Lithium
> secondary batteries, and then to compare that to the spot price. That
> would give some gauge as to cost per battery at baseline for just that
> component, which is the restricted resource (pretty much everything
> else is very common and very cheap. Iron and Phosphate, plastics).
>
> well, the US price for lithium (carbonate) got to $5500/tonne or so
> this year. So let's use that. That comes out to $2.75/lb. The amount
> of lithium metal in lithium carbonate is about 11/58. So that brings
> the Lithium metal cost to about $80 per lb (per 453.59 g).
>
> Then I found a paper that clearly stated: "The amount of lithium
> contained in a secondary lithium cell by weight is approximately 0.3g
> per AH" That assumes of course the base voltage of 3.7.
>
> So, a 50AH Lithium cell has ~15g of Lithium metal in it. Which comes
> out to about $2.65.
>
> I just thought that was very interesting :) Even if you tripled that
> cost (buying LiFePO4 from a manufacturer) it comes out to only $7.93
>
> Thundersky 40AH batteries are selling for $80.
>
> So if everything else in that battery cost $30 (which is quite high),
> they are still clearing quite a chunk of change. I realize...
> recouping costs, R&D, and so on. I just wanted to illustrate the basic
> costs.
>
> FYI.
>
> --T
>
--- End Message ---
--- Begin Message ---
Thank you for actually reading my posts Tehben
No problem ;)
Again I personally have not come to a conclusion either way as to the
safety of manmade electromagnetic fields.
Here is the conclusion of a study -1999 NIEHS Report on Health
Effects from Exposure to Power-Line Frequency Electric and Magnetic
Fields- done by the US government. (If you trust the Feds to tell you
what is good for you [which I personally don't])
Link: http://www.niehs.nih.gov/emfrapid/
If you don't want to read the whole thing it basically says that
there is no proof that ELF-EMF exposure has health risks from animal
testing and so on, but it also says (I quote) "The NIEHS concludes
that ELF-EMF exposure cannot be recognized as entirely safe because
of weak scientific evidence that exposure may pose a leukemia
hazard." - 4th paragraph down.
IEHS Conclusion
As part of the EMF-RAPID Program’s assessment of ELF-EMF-related
health effects, an international panel of 30 scientists met in June
1998 to review and evaluate the weight of the ELF-EMF scientific
evidence (12). Using criteria developed by the International Agency
for Research on Cancer, none of the Working Group considered the
evidence strong enough to label ELF-EMF exposure as a "known human
carcinogen" or "probable human carcinogen." However, a majority of
the members of this Working Group (19/28 voting members) concluded
that exposure to power-line frequency ELF-EMF is a "possible" human
carcinogen. This decision was based largely on "limited evidence of
an increased risk for childhood leukemias with residential exposure
and an increased occurrence of CLL (chronic lymphocytic leukemia)
associated with occupational exposure." For other cancers and for non-
cancer health endpoints, the Working Group categorized the
experimental data as providing much weaker evidence or no support for
effects from exposure to ELF-EMF.
The NIEHS agrees that the associations reported for childhood
leukemia and adult chronic lymphocytic leukemia cannot be dismissed
easily as random or negative findings. The lack of positive findings
in animals or in mechanistic studies weakens the belief that this
association is actually due to ELF-EMF, but cannot completely
discount the finding. The NIEHS also agrees with the conclusion that
no other cancers or non-cancer health outcomes provide sufficient
evidence of a risk to warrant concern.
The ultimate goal of any risk assessment is to estimate the
probability of disease in an exposed population. In general, this
involves the combination of three basic pieces of information: the
probability that the agent causes the disease, the response as a
function of exposure given that the exposure does cause disease and
the distribution of exposures in the population being studied. The
NIEHS believes that the probability that ELF-EMF exposure is truly a
health hazard is currently small. The weak epidemiological
associations and lack of any laboratory support for these
associations provide only marginal, scientific support that exposure
to this agent is causing any degree of harm.
The NIEHS concludes that ELF-EMF exposure cannot be recognized as
entirely safe because of weak scientific evidence that exposure may
pose a leukemia hazard. In our opinion, this finding is insufficient
to warrant aggressive regulatory concern. However, because virtually
everyone in the United States uses electricity and therefore is
routinely exposed to ELF-EMF, passive regulatory action is warranted
such as a continued emphasis on educating both the public and the
regulated community on means aimed at reducing exposures. The NIEHS
does not believe that other cancers or non-cancer health outcomes
provide sufficient evidence of a risk to currently warrant concern.
Several groups have attempted to determine the risk of childhood
leukemia in the general population under the unproven assumption that
ELF-EMF is truly causing this disease (317-319). If this assumption
were correct, these calculations generally suggest, on average, that
between 5% and 15% of childhood leukemias could be caused by
exposures to ELF-EMF with confidence intervals including 0%. Based
upon this assumption, our own evaluations using the most current data
and several different methods of analysis do not disagree with these
percentages. The risk of getting leukemia prior to age 15 in the
United States is about 0.05% (5/10,000 people)(320). This would make
the lifetime risk of childhood leukemia attributable to ELF-EMF
(again, conditional on the risk being real) between 2.5 to 7.5 per
100,000 people. On a yearly basis, this conditional risk is
approximately 15 times less than the lifetime risk or 2 to 6
additional cases per million children per year.
The National Toxicology Program routinely examines environmental
exposures to determine the degree to which they constitute a human
cancer risk and produces the "Report on Carcinogens" listing agents
that are "known human carcinogens" or "reasonably anticipated to be
human carcinogens." It is our opinion that based on evidence to date,
ELF-EMF exposure would not be listed in the "Report on Carcinogens"
as an agent "reasonably anticipated to be a human carcinogen." This
is based on the limited epidemiological evidence and the findings
from the EMF-RAPID Program that did not indicate an effect of ELF-EMF
exposure in experimental animals or a mechanistic basis for
carcinogenicity.
--- End Message ---
--- Begin Message ---
childreypa wrote:
I've been calling some forklift places trying to find an old motor that
I can use to get my project going. I am looking for a large forklift
motor at 48v. I mentioned that this was for an electric vehicle running
greater than 96v. The man said I couldn't do this. A 48v motor can only
handle 48v.
I'm sorry, but he is incorrect. It's done all the time. The motor will
run faster at higher voltage (of course), which is a problem in a fork
lift; but not for a vehicle you drive on the street.
Also, you're going to be using it with a controller which reduces the
pack voltage anyway. In a fork lift, you may often run at full throttle.
But a car spends almost all its time at far less than full throttle
(which means, the motor is far less than pack voltage).
How do I answer an oldtimer who knows plenty more than me
about motors that I want to use a 48v motor in an EV?
The tactful way is to say, "Thank you for the advice! I'll be sure to
keep the voltage down to 48v as you suggest." Then ignore it.
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
Ah, actually I was thinking IR like 38KHz TV remotes, not specifically IRDA.
You do generally need LOS. Just doing it in an enclosure without LOS
expecting reflections to carry it is very haphazard. Differences in
interior color make huge differences as does angling of the
transmitter. Any incidental sunlight can potentially overwhelm a
receiver. Making it so 10 transmitter-receivers can all see each other
would be pretty darn difficult. If one node can't receive from others
even though its transmitter could be seen by others, it might transmit
during the same time as the others. Depending on your protocol it might
well be possible for a node to figure out when it should xmit even
though it could only receive a coherent signal from one or two others.
So looking at all the things that can (and almost certainly will) go
wrong, just one gnd and one signal wire doesn't sound too hard to route
to each device.
Danny
(-Phil-) wrote:
Note, I didn't specify IIRDA!
I recommend 40khz IR. Same stuff used in consumer electronics for
remote controls. You don't need LOS. No cabling and you can pot the
whole assembly so no battery acid can get on your board or the data
connectors. Only cabling in the battery box will then be the primary
wiring.
-Phil
----- Original Message ----- From: "Danny Miller" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Sunday, May 13, 2007 12:04 PM
Subject: Re: BMS (Battery Management System (Was: 1-Wire Expertise)
I don't think there's any practicality to using IRDA. You generally
need a straight line-of-sight.
Again, the 1-wire protocol CAN be adapted to an isolated scheme,
however, no commercially available device will implement it. You'd
need to write up an implementation. It just takes a controller (PIC)
and two optoisolators (might be $1 or $2). So you can power a PIC
voltage sensor with the battery voltage and then communicate that
across the isolated bus.
There's a question of how much power the sensor draws. It's not much
but the important problem here is that with one hooked up to each
batt it's generally impractical to disconnect each one when you're
not driving. The PIC may be able to go into SLEEP mode and its
current goes way into inconsequential. However, the typical voltage
divider must remain powered and that draws about 2.5mA. The
optoisolator's receiving side also has a nonzero "dark current" when
the receiving side is powered even if it's at the "off" level.
Well, 2.5mA isn't a particularly big problem. It would take months
to use a substantial portion of the batt capacity.
The boards should logically integrate the charging regs on-board,
since we're already building one per batt.
Danny
(-Phil-) wrote:
I used the TSOP1740 in a project a few years ago. I think I bought
100 of them for about 40 cents each. Pretty cheap!
http://www.vishay.com/docs/82030/82030.pdf
You may be thinking of FastIR/IRDA or similar. Too costly, and no
need to invoke the complex protocols.
The Micros can be very small/low power. The protocol is very
simple because of the low data rate requirement. I can do it in a
few hundred lines of assembly code, and run it on a ring-clocked low
power micro.
It's probably easier, cheaper, and more reliable to use IR rather
than visible. The components ate cheap, and the modulated IR will
bounce better and not suffer as many from problems from
interference. They work fine even in the presence of sunlight.
If I build it, I will open-source it. Hurray if others want to
build them using my code! If more DIY EV'ers had a BMS, we'd save
a lot of batteries!
-Phil
----- Original Message ----- From: "Lee Hart" <[EMAIL PROTECTED]>
To: <ev@listproc.sjsu.edu>
Sent: Saturday, May 12, 2007 2:26 AM
Subject: Re: BMS (Battery Management System (Was: 1-Wire Expertise)
This is a good idea, Phil. I've used visible light in a battery
box, and it worked pretty well. The box had white styrofoam lining
it, and the light bounced around nicely, so a single sensor could
see the light from any sender.
I wonder about the cost, though. The IR receivers I see cost
dollars, not pennies. Do you have any examples in mind? Also, the
micro may need to be more powerful than you think; network
protocols often require a large amount of computing resources.
An open source project is a worthy goal, but too often people use
the name to mean, "I want somebody else to develop it for me for
free." I'm not sure how to inspire a group of people to work
together on such a project.
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377,
leeahart_at_earthlink.net
(¤Phil¤) wrote:
Seems like the right thing to do is put a little board on each
battery. The board would contain a small microcontroller with ADC,
a IR LED, a monolithic IR receiver (like those used in consumer
electronics to receive remote control signals), a high-current
MOSFET and a resistor (light bulb?). The board would only hook to
(+) and (-) of each battery in the array. No data cabling. 2
wires, that's it.
The units would all be identical, but contain a unique serial
number in the firmware. A central controller would then poll the
individual units via 40khz IR signals. The units would respond
the same way. The central controller can then order the load on
and off for equalization of the pack when charging.
The IR effectively galvanically isolates the whole mess and makes
it unlikely an accident could occur. The IR would readily bounce
all around battery enclosures and make a reliable 2-way
communication system with no wires and very low cost. The IR
LED/Receiver are commodity items and cost pennies.
The little boards would thus be cheap and easy to make, and very
safe with no possibility of shorts, etc.
Open-source the firmware and PCB design. Maybe a group-buy of the
little PCBs.
--- End Message ---
--- Begin Message ---
Hi Ian and All,
Ev's are very eff but as you can imagine,
some are more than others. Conversions are not the best as
they carry so much extra weight and you need more
batteries, power based mostly on weight. So the more weight,
the more wthrs/mile though once above 45 mph, aero drag
bites big time.
For these and many older conversion EV's, from
the wall they go from 100wthrs/mile for John Bryan's Karman
Ghia because it's light, aero and he worked hard deleting
drag to 1,000wyhr/mile for some large truck/SUV conversions.
Most car conversions get from 200-400wthrs/mile.
But to really judge EV's, you need to look at
the built as an EV like the EV-1 which got around
175wthrs/mile or other custom builts like the Sundancer EV,
the Selectria Sunrise, ect, that do better than that. Some
of the old aero dead kitcars can be found cheap, under $1k
many times, would make a great EV at a very reasonable cost.
Personally I expect my 1300lb aero 2 seat
EV's to do under 100wthr/mile except for high speed cruising
as my Ewoody did with much worse aero but I rarely went over
45 mph in it. It, as all wthr/mile should be measured with a
house meter which is a cheap, accurate way to measure as it
gets the charging eff too or other good method. Average 5 or
so charges and you have a accurate number.
Nice custom very lightweight, aero EV's can
get under 50wthr/mile.
So if you want a cost effective, successful
EV, keep weight, aero in mind.
BTW 100wthr/mile is equal to 300mpg cost wise
at $.10kwhr, 160-400mpg equivilent depending on the electric
source eff.
Jerry Dycus
----- Original Message Follows -----
From: Ian Hooper <[EMAIL PROTECTED]>
To: ev@listproc.sjsu.edu
Subject: Vehicle efficiency, wh/mile
Date: Sun, 13 May 2007 17:32:37 +0800
>Hi all,
>
>I was just curious if many people on the list have measured
>their EV's efficiency i.e average watt-hours per mile?
>
>I've heard figures around 300wh/mile thrown around, but
>that seems like a fair bit of energy to me.. Could that
>be based on people using the C20 capacity of lead acid to
>calculate the pack's energy?
>
>-Ian
>
--- End Message ---
